This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. During early embryogenesis, a single totipotent zygote gives rise to multiple identical blastomeres. After this stage, cells are segregated to develop the pluripotent inner cell mass (ICM), from which mouse and human embryonic stem (ES) cells are derived. Because ES cells mirror the pluripotent stem cell functions both in vitro and in vivo, they can be used as model systems to understand the mechanisms underlying basic cell-cell interactions in early mammalian embryos. However, availability of such embryonic stem cells is limited and there are also ethical considerations regarding their use. Recent studies have found that expression of four stem cell-specific genes in skin cells obtained from skin biopsy is sufficient to generate patient-specific iPSC for use in transplantation for tissue regeneration. However, there remains a major technical concern with the use of these cells clinically as use of virus to express stemness genes in the patient's cells runs a risk for introduction of cancer. Because of this, we have tried to develop a protocol for converting differentiated somatic cells to iPSC by inducing expression of endogenous stem cell genes through sphere formation in vitro. The purpose of this work is to investigate and optimize iPSC production using a novel technique to force somatic cells to form spheres, which triggers dramatic reprogramming of cells back to a stem cell phenotype.